Magnetic bistable device and control system using such devices



Feb. 20, 1968 F. J. J. HENDRICKX 3,370,278

I MAGNETIC BISTABLEDEVICE AND CONTROL SYSTEM USING SUCH DEVICES FiledOct. 25, 1963 2 Sheets-Sheet 1 1nvenlor I FRA/VC/SCUS J. \l, HEIVOR/C'KXUnited States Patent MAGNETIC BISTABLE DEVICE AND CONTROL SYSTEM USINGSUCH DEVICES Franciscus J. J. Hendrickx, Antwerp, Belgium, assignor toInternational Standard Electric Corporation, New York, N.Y., acorporation of Delaware Filed Oct. 23, 1963, Ser. No.-318,270 Claimspriority, application Netherlands, Nov. 12, 1962, 285,390 7 Claims. (Cl.340-474) The present invention relates to a magnetic device comprisingat least one magnetic element having at least two stable conditionswhich are determined in association with at least one magnetizing sourcehaving two possible output conditions.

A magnetic stable device of this general type is disclosed in US. Patent2,770,796 (H. Boer), granted Nov. 13, 1956, wherein the magnetic elementis one which is normally not magnetized and which is subjected to thefield produced by said magnetizing source in order to register, by themagnetization produced therein, the condition of the magnetizing source.Such magnetization, however, requires a relatively large magnetic fieldby virtue of the absence of physical contact between the magnetizingsource and the magnetic element, and also due to the high impedancepresented by the latter to the magnetic energy of the former.

It is therefore an object of the present invention to provide a magneticdevice of the above type wherein the condition of a relatively weakmagnetizing source can be reliably registered in said magnetic element.

The present magnetic device is characterized by the provision of amagnetic element which is mounted for rotation. This element is apermanent magnet having 2m(m l) poles, which, when moved into proximityto said magnetizing source in one or the other source condition, iseither angularlydisplaced or remains stationary so that the part thereofwhich is nearest to said magnetizing source exhibits a pole having apolarity opposite the one exhibited by the proximate part of saidmagnetizing source. The device further includes holding means adapted tocoact with said magnetic element for maintaining the latter inpredetermined angular positions.

The present magnetic device is also characterized in that said holdingmeans comprises an auxiliary element which is a permanent magnet having2m(m21) poles and which is rotatably mounted in close proximity to themain magnetic element.

One advantage of such devices is that they have a more universal rangeof application. Foremost'however, as in the above-mentioned U.S. Patent2,770,796, the present devices are most advantageously applied toarrangements wherein code indications registered by the magneticelements therein are conveyed between different locations. 7

The present control system, to be disclosed herewith, employs magneticdevices of the above described type and features coding means each ofwhich comprises a magnetizing source having two possible conditions andeach coacting with pairs of main and auxiliary permanent magnetelements, each having 2m(m 1) poles which are rotatably mounted in closeproximity to each other. Upon a magnetic register element being coupledto a magnetizing source, the main and auxiliary permanent magnetsconstituting a magnetic register element are either both angularlydisplaced, or both remain stationary, whereby the part of the mainpermanent magnet which is nearest to said magnetizing source exhibits apole having a polarity which is opposed to the one exhibited by thenearest pole of said magnetizing source.

The above mentioned and other objects and features of the invention willbecome more apparent and the invention itself will be best understood byreferring to the following description of embodiments taken inconjunction with the accompanying drawings in which:

FIG. 1 represents a magnetic bistable device according to the invention;

FIG. 2 shows a detecting means included in a control system according tothe invention;

FIG. 3 represents a control system according to the invention.

Principally referring to FIG. 1 the present magnetic bistable deviceincludes a magnetizing source 1 and two annular permanent magnets 2 and3. The magnetizing source 1 includes a core 4 on which is wound awinding 5 which is coupled to a DC source 6 via change-over contacts 7and 8. The main and auxiliary magnetic elements 2 and 3 respectively,are supported by and freely rotatable about the rigid wires 9 and 10which pass through their respective centers. The change-over contacts 7and 8 form part of a manually operable key (not shown) which has twostable positions, namely a rest position wherein the contacts 7, 8 arein the position shown in FIG. 1 and an operative position wherein thesecontacts are in the opposite work position. In the following discussionit is assumed for reference purposes that, in the rest position of thenot shown key, the core 4 is so magnetized that its lower end exhibits anorth pole.

Each of the magnetic elements 2, 3, may have 2m poles, where m is anyinteger greater than zero, but in the following it is assumed that onlytwo-pole elements are employed, one radial half of the element formingone pole and the other radial half constituting the other pole.

It should further be observed that the magnetic elements 2, 3 of eachcouple of such elements are closely mounted next to each other so thatunder static, or

stable, conditions, facing poles thereof are necessarily of opposite, orattracting, polarities, since poles of like polarity would tend to repeleach other and thereby tend to produce a rotation of the elements.

The above magnetic bistable device operates as follows. Suppose that themain and auxiliary magnetic elements 2, 3 are in the positions showni.e. both have their south pole directed towards the core 4. The southpole of the magnetic element 2 is then strongly attracted by the northpole at the lower edge of core 4 when the contacts 7, 8 are in thenormal rest position. When an operator sets the above-mentioned key tothe active position, the contacts 7, 8 travel to their active positionsand due to this the core 4 is magnetized so as to exhibit a south poleat its lower end. This south pole tends to repel the south pole of themagnetic element 2 and the latter, being freely rotatable, tends topivot about the rigid wire 9 in the sense indicated. This rotation willhowever be counteracted by the attractive force existing between thenorth pole of the main magnetic element 2 and the south pole of theauxiliary magnetic pole element 3. The magnetizing source 1 and themagnetic elements are so chosen that, notwithstanding the action of theauxiliary magnetic element 3, the chain magnetic element 2 starts topivot and as the south pole of the main magnetic element 2 approachesthe south pole of the auxiliary magnetic element 3, the latter will berepelled and will start pivoting in the sense indicated. Finally themain and auxiliary magnetic elements 2, 3 will come to rest in aposition wherein the north poles of both elements are directed towardsthe active south pole of core 4 of the magnetizing source 1.

From the above it follows that, depending upon the position of the notshown key mentioned above, and hence of the change-over contacts 7, 8controlled by that key, the couple of magnetic elements 2, 3 -can be setto one of two stable conditions. It may also be noted that the conditionof the magnetizing source remains stably registered in the associatedcouple of magnetic elements when the latter are moved out of the rangeof influence of the former. Should the source be in the -condition whenthe magnetic elements are coupled thereto, the magnetic elements arealso set to the O-condition, their south poles being directed towardsthe core 4 of the source. On the other hand, if the source is in thel-condition, the contacts 7, 8 being then in their active positions, themagnetic elements are also set to the l-condition, their north polesbeing directed towards the core 4 of the source.

As explained above, the auxiliary magnetic element 3 initially impedesthe rotation of the main magnetic element 2 and then rotates therewith.Hence this auxiliary magnetic element 3 constitutes a holding means forthe main magnetic element and prevents the latter from pivoting from the0-position to the 1-position under the influence of forces other thanthose produced by the magnetizing source 1. If the main magnetic elementhas 2 poles and is subjected to such an extraneous force, the elementwill be set to a new condition only if the extraneous force causes theelement to undergo a rotational displacement of 180. For an elementhaving 4 poles this safety margin would become equal to 90, etc. i.e.the safety margin becomes smaller as the number of poles is increased.

As may be seen with reference to FIG. 1, the plane AA passing throughthe centers of the stationary magnetic elements 2, 3 should not bealigned with the extension of the median plane BB through the core 4,since, in the latter case, the magnetic force vector resulting from thefields produced by the magnetizing source 1 and the magnetic element 2passes through the center of the element 2 and would hence not produce atorque to pivot the latter.

Obviously such a precaution is not necessary if the. magnetic elements2, 3 are moved relative to the magnetizing source 1, in which eventthere are a plurality of positions wherein the above resultant magneticforce vector does not pass through the center of the magnetic ele ment2, and an element in the O-state will always tend to pivot to thel-state when the switch is in the active position.

Principally referring to FIG. 2, there is shown a detecting means fordetecting the condition which has previously been registered in themagnetic elements 2, 3. This detecting means is constituted by a reedswitch comprising contacts 11-12 which is mounted in a sealed envelope13 and close to which is mounted a permanent magnet 14 which exhibitsnorth and south poles at its upper and lower ends respectively, thissouth pole facing the upper part of the reed 11. The attraction forceproduced by themagnetic field of the permanent magnet in the gap wherethe reeds 11 and 12 face each other is supposed to be insufficient torealize the contact between these reeds. Due to this, the contacts 11-12is normally open and it may be said that the permanent magnet polarizesthe reed switch 13 in a predetermined or 0-condition.

When a couple of magnetic elements 2, 3 which are in the O-condition,i.e. with their south poles directed towards the reed switch 13, isoperatively associated with this reed switch, the latter will not beclosed. Indeed, the force produced in the above gap by the magneticfield of the magnetic element 2 is opposite to that produced in this gapby the magnetic field of the permanent magnet 14 and is supposed not tobe sufliciently strong to create an inverse field large enough toproduce an attraction force between the reeds 11-12 to bring them intocontact with each other.

On the contrary, when this couple of magnetic elements 2, 3 is in thel-condition, i.e. with their north poles directed towards the reedswitch 13 as shown, the attraction force produced in the above gap bythe magnetic field of the magnetic element 2 acts in the same sense asthe force produced in this gap by the magnetic field of the permanentmagnet 14. It is supposed that this sum of forces is sufficient toattract the reeds 11 and 12, thus closing the reed switch.

It should be noted that the reed switch is preferably of the wettedcontact type, such a type permitting an extremely high number ofoperations before it begins to deteriorate.

In a preferred embodiment, the magnetizing sources 1 and the magneticelements 2, 3 are disposed as shown in FIG. 1 and conveying means areprovided for displacing these elements towards detecting means such asshown in FIG. 2 along a horizontal plane aa which is perpendicular tothe median plane B--B of the core, or along a cylindrical surface.

In the United States Patent No. 2,873,863, granted Feb. 17, 1959 to G.X. Lens, a control system is described in which a plurality of coderegisters are mounted on an endless main conveyor, for the purpose ofconveying code signals from a fixed mechanism, operated from anoperators keyboard, to control conveying and sorting apparatus. Thereinan intermediate endless conveyor is interposed, at each input station,between the fixed mechanism and the main conveyor. This intermediateconveyor is provided with one or more intermediate registers regularlyspaced, which transfer the code indication of the fixed mechanism to theregisters on the main conveyor. The auxiliary conveyor permits the fixedmechanism to register a given code during a time substantiallyindependent of the number of inputs. In other words, the maximum codingtime is given to the operator controlling the keyboard.

The code registers on the main conveyor and the intermediate coderegisters are mechanically operated, so that they are subjected to wear.Another disadvantage of this known control system is that it requires amechanism having an epicyclic pattern of movement, on which are mountedthe intermediate registers, for subjecting the latter to a translationmovement only and for ensuring a proper cooperation with the registerson the main conveyor for the transfer of the registered code.

The above described magnetic bistable device and detecting means mayadvantageously be used in a control system of the type disclosed in theabove Patent 2,873,863. This will become clear from what follows,reference being had, for this purpose, to FIG. 3 which shows a mainconveyor 15, a number of code registers 16, an intermediate register 17,a coding circuit 18 which is operated from an operators keyboard (notshown) and a detecting station 19.

It is, for instance, supposed that an operator is required to direct thesorting of goods, e.g. letters, to one of 1000 possible destinationsnumbered 0 to 999. Therefore the keyboard of the operators stagecomprises three sets each having ten keys, these sets of ten keys beingused for selectively recording the respective units, tens and hundredsdigits of a destination.

It is further supposed that each destination is to be translated in aZ-out-of-S binary code. Therefore each key controls two out of fivepairs of change-over contacts, each such pair constituting part of amagnetizing source of the type shown in FIG. 1. In other words, each keyis able: to set two out of five magnetizing sources to the l-condition.To each set of ten keys are associated a set of fivemagnetizing sources,and each key of a set controls a different pair of magnetizing sourcesof the associated set according to the above 2-out-of-5 binary code. Thethree sets of five magnetizing sources, of which only one source isshown, are mounted next to each other above and transversely withrespect to the direction of movement of the conveyor 15.

The intermediate conveyor 17 comprises a drum 20 which is rotatableabout an axis 21 in the direction shown and which carries a number ofpairs of rigid Wires such as 22, 23, this number being equal to thenumber of operators. The wires 22, 23 extend parallel to the rotationaxis 21 of the drum which is parallel to the conveyor 15 andperpendicular to the direction of displacement thereof.

On each of the wires 22, 23 are threaded three sets of five magneticelements such as 24, 25, the elements 24 being the main ones and theelements 25 being auxiliary or holding ones. The threaded magneticelements are all identical and may for instance have a diameter of 20mm., and a spacing between successive elements, on the same wire, on theorder of 25 mm.

On the main conveyor 15 is mounted a support 26 carrying a plurality ofparallel rigid wires such as 27, 28 which are situated parallel to theconveyor 15 and which extend transversely thereto. On each of the wires27, 28 are threaded three sets each including five magnetic element suchas 29, 30, elements 29 being the main ones and elements 30 being theauxiliary or holding ones. These magnetic elements may for instance eachhave a diameter of 12 mm., with a spacing of.25 mm. between successiveelements on any wire, and with a separation between successive wires 27,of 40 mm.

The detecting station 19 includes 1000 groups of detecting means, eachsuch group being disposed above and transversely with respect to theconveyor 15. Each group of detecting means comprises three pairs of reedswitches of the type shown in FIG. 2 which are positioned so as torespond simultaneously to the three particular pairs of code bits whichcharacterize the corresponding destination as manifested by the elements29 on the main conveyor 15. The six reed switch contacts such as 11, 12of each of the 1000 groups are connected in series with the win-ding ofa corresponding one of 1000 electromagnets 31, across the poles of a DCsource (not shown). In this manner the electromagnet 31 will be operatedonly if all six reed switches in series with its winding have beenoperated simultaneously, and this ocurs only when the associated codesignal combination is applied to the reed switches.

The operation of the control system shown in FIG. 3

is as follows. Upon an operator having read a particular destination, heoperates three keys in the above-noted keyboard, namely one each in theunits, tens and hundreds sets of keys. Due to this, six magnetizingsources in the associated group of 15 magnetizing sources are set to the1-condition. Hence, when an intermediate register, i.e. a row of 15magnetic elements such as 24, is rotated towards the row of magnetizingsources, six of the magnetic elements will be set to the l-condition inthe manner described in relation to FIG. 1. In-this l-condition, thenorth poles of the six selected elements are directed towards the lowerpoles of the activating magnetizing sources. As the drum continuesrotating all of the elements remain fixed in position due to theinterlocking action between each couple of elements 24, 25.

When the above row of 15 magnetic elements, having six elementsselectively set to the l-condition, now approaches a row of 15 magneticelements 29 of a register on the main conveyor 15, six correspondingelements of the latter register will assume the l-condition in, a manneranalagous to that described in relation to FIG. 1 on condition that themagnetic forces exerted by the elements 24, 25 are greater than thoseexerted by the elements 29, 30. In the l-condition, the north poles ofthe latter six elements are directed upwardly. When the magneticelements of the register on the main conveyor are finally passed underthe 1000 groups of reed switches of the detecting station, it is clearthat one and only one of these groups will have all of its reed contactssimultaneously operated. Hence the electromagnet 31 associated to thisgroup, which controls the sorting transfer of a conveyed article to aparticular output destination, will be energized.

From the above it follows that in the control system of FIG. 3 thetransfer of codes is performed without frictional mechanical contact sothat in comparison to the control system of the Belgian Patent 552,139the wear is considerably reduced. Also the endless intermediate conveyorneed only be given a circular motion instead of an epicyclic one.

While the principles of the invention have been described in connectionwith specific apparatus, it is to be clearly understood that thisdescription is made only by way of example and not as a limitation onthe scope of my invention.

I claim:

1. A magnetic device comprising a permanent magnetic element having atleast two poles,

a magnetic source having two possible conditions of magnetization, meanssupporting said element for rotation relative to a given axial referenceon said supporting means,

further supporting means supporting said element and said supportingmeans for coupling said element to said magnetizing source to situatesaid element in an angular position determined by the state ofmagnetization of said source, and holding means mounted on said'furthersupporting means for cooperating with said magnetic element to stablyretain the latter in said position determined by said source, saidholding means comprising an auxiliary rotatably mounted magnetic elementwhich is a permanent magnet having at least two poles and which ismounted in close proximity to the main magnetic element. 2. Magneticbistable device as claimed in claim 1, characterized in that said mainand auxiliary permanent magnets are identical. 7

3. Magnetic bistable device as claimed in claim 1, characterized in thatsaid magnetizing source and said magnetic element are so disposed withrespect to each other that the magnetic force vector which results fromthe fields produced by said magnetizing source and said magnetic elementis not confined to the center of said magnetic element.

4. Control system, for registering and detecting information, comprisingone or more sets of fixedly mounted coding means for coding information,

a plurality of sets of magnetic register elements mounted'forcooperation with said sets of coding means,

one or more sets of fixedly mounted detecting means including a contactwhich is polarized by means of a permanent magnet for detecting the thuscoded information. and

conveying means for conveying said magnetic register elements from saidcoding means towards said de tecting means,

each of said coding means comprising a magnetizing source having twopossible conditions,

each of said magnetic register elements comprising a magnetic coupleincluding rotatably mounted main and auxiliary permanent magnets, eachhaving at least two poles which are mounted in close proximity to eachother, and

each said magnetic register element being effective,

when operatively associated with one of said magnetizing sources, toassume a corresponding condition in which the main and auxiliary magnetsthereof are both either angularly displaced to a new position or fixedin position, whereby the polarity of the pole of the main permanentmagnet which is nearest and interlaced in such a way that the distancebe:

tween two code registers which successively receive information from thesame set of coding means is equal to the distance between successivecode registers multiplied by the number of sets of coding means, that anintermediate endless conveyor is interposed be tween each set of codingmeans and said main conveyor, this intermediate conveyor being providedwith one or more intermediate code registers regularly spaced, whichregister the code of the coding means to transfer it to said coderegisters on said main conveyor, the motion of the auxiliary conveyorbeing synchronized with that of the main conveyor so that eachintermediate code register cooperates with a corresponding code registeron said main conveyor. 6. Control system as claimed in claim 5,characterized in that driving means are provided for imparting to saidintermediate conveyor a circular motion.

7. Control system as claimed in claim 5, characterized in that the mainand auxiliary permanent magnets, included in said main and intermediaecode registers are identical and that the main and auxiliary permanentmagnets included in said intermediate code registers are larger thanthose included in said main code registers.

1. A MAGNETIC DEVICE COMPRISING A PERMANENT MAGNETIC ELEMENT HAVING ATLEAST TWO POLES, A MAGNETIC SOURCE HAVING TWO POSSIBLE CONDITIONS OFMAGNETIZATION, MEANS SUPPORTING SAID ELEMENT FOR ROTATION RELATIVE TO AGIVEN AXIAL REFERENCE ON SAID SUPPORTING MEANS, FURTHER SUPPORTING MEANSSUPPORTING SAID ELEMENT AND SAID SUPPORTING MEANS FOR COUPLING SAIDELEMENT TO SAID MAGNETIZING SOURCE TO SITUATE SAID ELEMENT IN AN ANGULARPOSITION DETERMINED BY THE STATE OF MAGNETIZATION OF SAID SOURCE, ANDHOLDING MEANS MOUNTED ON SAID FURTHER SUPPORTING MEANS FOR COOPERATINGWITH SAID MAGNETIC ELEMENT TO STABLY RETAIN THE LATTER IN SAID POSITIONDETERMINED BY SAID SOURCE, SAID HOLDING MEANS COMPRISING AN AUXILIARYROTATABLY MOUNTED MAGNETIC ELEMENT WHICH IS A PERMANENT MAGNET HAVING ATLEAST TWO POLES AND WHICH IS MOUNTED IN CLOSE PROXIMITY TO THE MAINMAGNETIC ELEMENT.